The present invention relates to a novel water-repellent composition, and particularly to a water-repellent composition having excellent water resistant properties and improved handling properties.
Although conventional gypsum boards have excellent characteristics such as high fire resistant properties, high sound-proof properties, and low price, such boards have a disadvantage in that the water resistant properties are rather poor, and thus its application is limited. To provide gypsum with water-repellent properties, an aqueous emulsion of, for instance paraffin waxes, petroleum resins, or higher fatty acids, has been used, and especially paraffin waxes are often used because of excellent water-repellent properties and low price. However, as a large amount of surfactant must be added to emulsify paraffin waxes, the surfactant remains in gypsum boards in a great amount, which deteriorates their water-repellent properties.
In order to overcome such a defect, it is proposed to use, as a water-repellent agent, for instance a composition containing paraffins and oxidized paraffins (Japanese Patent Publication No. 55-50906), a composition containing waxes and waxes containing carboxyl groups (Japanese Laid-open Patent Application No. 55-37423), and a composition containing waxes and a monoester of styrene/maleic anhydride copolymer (Japanese Patent Publication No. 58-58304).
These water-repellent compositions, however, can not exhibit their characteristics to full extent unless such compositions are added in large amounts and have insufficient mechanical stability and storage stability. Additionally, a slurry of gypsum becomes unstable.